On Sun, Jan 15, 2017 at 06:01:05PM +0100, Ilya Dryomov wrote: > On Sun, Jan 15, 2017 at 8:45 AM, <caifeng.zhu@xxxxxxxxxxx> wrote: > > Hi, all > > > > Let's look at the problem first. We have a lot of 'bad crc in data' > > warnings at OSDs, like below: > > 2017-01-14 23:25:54.671599 7f67201b3700 0 bad crc in data 1480547403 != exp 3751318843 > > 2017-01-14 23:25:54.681146 7f67201b3700 0 bad crc in data 3044715775 != exp 3018112170 > > 2017-01-14 23:25:54.681822 7f67201b3700 0 bad crc in data 2815383560 != exp 1455746011 > > 2017-01-14 23:25:54.686106 7f67205da700 0 bad crc in data 1781929234 != exp 498105391 > > 2017-01-14 23:25:54.688092 7f67205da700 0 bad crc in data 1845054835 != exp 3337474350 > > 2017-01-14 23:25:54.693225 7f67205da700 0 bad crc in data 1518733907 != exp 3781627678 > > 2017-01-14 23:25:54.755653 7f6724115700 0 bad crc in data 1173337243 != exp 3759627242 > > ... > > This problem occurs when we are testing(by fio) an NFS client, whose NFS server is > > built on an XFS + RBD combination. The bad effect of the problem is that: OSD will close > > the connection of crc error and drop all reply messages sent through the connection. > > But the kernel rbd client will hold the requests and wait for the already dropped > > replies which will never come. A deadlock occurs. > > > > After some analysis, we suspect write_partial_message_data may have a race condtion. > > (Code below is got from gitbub.) > > 1562 page = ceph_msg_data_next(cursor, &page_offset, &length, > > 1563 &last_piece); > > 1564 ret = ceph_tcp_sendpage(con->sock, page, page_offset, > > 1565 length, !last_piece); > > ... > > 1572 if (do_datacrc && cursor->need_crc) > > 1573 crc = ceph_crc32c_page(crc, page, page_offset, length); > > At line 1564 ~ 1572, a worker thread of libceph workquue may send the page out by TCP > > and compute the CRC. But simultaneously, at the VFS/XFS level, there may be another thread > > writing to file position cached by the sending-out page. If page sending and crc compution > > is interleaved by data writing, bad CRC will be complained by the receiving OSD. > > > > To verify our suspection, we add the debug patch below: > > (Code below is based on our linux version.) > > ... which is based on? This should be fixed in 4.3+ and all recent stable > kernels. > We are using CentOS 7.1, with kernel as kernel.osrelease = 3.10.0-229.14.1.el7.1.x86_64. With patches added by CentOS, the ceph kernel client is roughly about 4.0~. Is there any info or doc about the fixes in 4.3+? Thanks in advance. > Thanks, > > Ilya > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
